Effects of Melatonin and Dexamethasone on Facial Nerve Neurorrhaphy

Evaluation of the Effect of Platelet-Rich Plasma Injection After Recurrent Nerve Injury in Rats

Introduction

Injuries to the recurrent laryngeal nerve (RLN) that may occur during thyroidectomy cause hoarseness, dysphagia, and dyspnea. Even if the injured nerve can be repaired surgically, it heals slowly and not completely. Platelet-rich plasma (PRP) is obtained by centrifuging blood taken from the human body. PRP accelerates the healing of the injured nerve due to the many growth factors it contains. The aim of this study is to investigate the therapeutic effectiveness of PRP and assess surgical repair after RLN injury.

Materials and Methods

Twenty-eight male Wistar albino rats were used in this study. We divided the rats into four groups, with seven animals in each group. Group 1: RLN was cut and primary repair was performed. Group 2: RLN was cut but not repaired. Group 3: RLN was cut, primary repair was performed, and PRP was injected. Group 4: RLN was cut, and PRP was injected without repair. Laryngoscopy and electromyography (EMG) were conducted before and after the procedure. For histopathological evaluation, parameters such as Schwann cell count, axon damage, and immunohistochemical staining intensity of Ki-67 cell proliferation marker were examined.

Results

The highest amplitudes in EMG were seen in Group 3 rats at the third- and sixth-week postoperatively (p < 0.05). Regarding histopathological evaluation, Schwann cell count, and Ki-67 immunohistochemical staining were primarily observed in Group 3 rats (p < 0.05). Axonal damage and cytoplasmic vacuolization were minimally detected in Group 3 rats (p < 0.05).

Conclusion

In our experimental rodent model, PRP injection increased the Schwann cell count and cell proliferation rate in the injured RLN area by promoting the healing of nerve axons.

Melatonin and Methylprednisolone Combination Ameliorates Inflammation and Enhances Recovery After Sciatic Nerve Crush Injury

This sham-controlled animal study aimed to investigate the effects of melatonin and methylprednisolone combination on motor function, nerve conduction and histopathological and biochemical findings in rats with sciatic nerve crush injury. Forty-eight male Sprague-Dawley rats were divided into 6 groups (n = 8): CT: control, VEH: sciatic nerve injury, LMP: 15-mg/kg methylprednisolone, high-dose methylprednisolone (HMP): 30-mg/kg methylprednisolone, MEL: 15-mg/kg melatonin, MMP: 15-mg/kg methylprednisolone+15-mg/kg melatonin. The rats were evaluated with Sciatic Functional Index (SFI), nerve conduction study, interleukin-1β (IL-1ß), nerve growth factor (NGF), total antioxidant status (TAS), total oxidant status (TOS) and histopathological scores. There were no significant intergroup differences in baseline tests. SFI significantly improved in all treated groups with no significant intergroup differences. Motor amplitude improved most in MMP, LMP and MEL, respectively. Nerve conduction velocity significantly improved in MMP compared to VEH. There were no significant intergroup differences regarding serum NGF, TAS and TOS. Tissue NGF levels were higher in LMP, HMP and MEL. IL-1ß levels were significantly lower in CT and MMP. Tissue oxidative stress levels were significantly lower in treated groups compared to VEH, with no significant difference among them. MMP showed greater histopathological improvement. Melatonin combination therapy in sciatic nerve crush injury provided adequate functional improvement, superior electrophysiological and histopathological recovery compared to high-dose methylprednisolone and exhibited better anti-inflammatory activity through IL-1ß.

Effect of Melatonin Administration on Nerve Regeneration after Recurrent Laryngeal Nerve Injury

Recurrent Laryngeal Nerve (RLN) injury is a complication in neck surgery. The aim of this study is to evaluate the effect of primary suture repair with melatonin treatment on nerve regeneration after RLN damage. After the RLN damage, nerve repair was performed in the first and fourth groups. The third and fourth groups were given intraperitoneal melatonin therapy daily for six weeks. EMG was applied to all subjects and vocal cord movements were evaluated endoscopically. At the end of the sixth week, all subjects were sacrificed, and their larynx were examinedhistologically. Vocal cord paralysis (VCP) was observed in all subjects after RLN damage. In the sixth week, improvement was observed in the first and fourth group who underwent nerve repair, whereas none in the second and third group, who did not undergo nerve repair, improved. With EMG, the highest MUP was in the fourth group. Histologically, an increase in Schwann cells, a decrease in axon damage, and cytoplasmic vacuolization were in the fourth group. Myelin protein zero and Ki-67 staining were the most in the fourth group. In our study, laryngoscopic, electrophysiological and histopathological findings show that melatonin contributes to nerve healing but this could not translate into functional recovery.

Electrophysiological and histopathological evaluation of the effectiveness of melatonin and glatiramer acetate for traumatic facial nerve injuries

AIM

This study aimed to evaluate the effect of systemic/local use of melatonin and glatiramer acetate on regeneration in traumatic nerve injury models.

MATERIALS AND METHODS

A total of 42 male Wistar albino rats were randomly divided into 6 groups: healthy control (Group 1), injured control (Group 2), local melatonin (Group 3), systemic melatonin (Group 4), local glatiramer acetate (Group 5), and systemic glatiramer acetate (Group 6). In all groups, electromyography recordings of the facial nerve were obtained after surgery and before sacrifice, and the damaged nerve region was histopathologically examined after sacrifice.

RESULTS

In the electrophysiological evaluation, the control group had the greatest decrease in amplitude and extension in latency time following surgery than the treatment groups. Furthermore, a significant decrease in the degenerative axon count, edematous areas, and fibrotic areas as well as a significant increase in axonal surface areas was observed in all the treatment groups compared with the damage control group.

CONCLUSIONS

Although both glatiramer acetate and melatonin are beneficial in regeneration in traumatic facial nerve injuries, it can be concluded that systemic use of melatonin can yield more positive results than glatiramer acetate and local use of both two drugs.

Facial nerve regeneration via body-brain crosstalk: The role of stem cells and biomaterials

The human body is a complex, integral whole, and disruptions in one organ can lead to dysfunctions in other parts of the organ network. The facial nerve, as the seventh cranial nerve, arises from the brainstem, controls facial expression muscles and plays a crucial role in brain-body communication. This vulnerable nerve can be damaged by trauma, inflammation, tumors, and congenital diseases, often impairing facial expression. Stem cells have gained significant attention for repairing peripheral nerve injuries due to their multidirectional differentiation potential. Additionally, various biomaterials have been used in tissue engineering for regeneration and repair. However, the therapeutic potential of stem cells and biomaterials in treating facial nerve injuries requires further exploration. In this review, we summarize the roles of stem cells and biomaterials in the regeneration and repair of damaged facial nerves, providing a theoretical basis for the recovery and reconstruction of body-brain crosstalk between the brain and facial expression muscles.

An in vitro model for postoperative cranial nerve dysfunction and a proposed method of rehabilitation with N-acetylcysteine microparticles

PURPOSE

When operating near cranial motor nerves, transient postoperative weakness of target muscles lasting weeks to months is often observed. As nerves are typically intact at a procedure's completion, paresis is hypothesized to result from a combination of neurapraxia and axonotmesis. As both neurapraxia and axonotmesis involve Schwann cell injury and require remyelination, we developed an in vitro RSC96 Schwann cell model of injury using hydrogen peroxide (H2O2) to induce oxidative stress and investigated the efficacy of candidate therapeutic agents to promote RSC96 viability. As a first step in developing a long-term local administration strategy, the most promising of these agents was incorporated into sustained-release microparticles and investigated for bioactivity using this assay.

METHODS

The concentration of H2O2 which reduced viability by 50% was determined to establish a standard for inducing oxidative stress in RSC96 cultures. Fresh cultures were then co-dosed with H2O2 and the potential therapeutics melatonin, N-acetylcysteine, resveratrol, and 4-aminopyridine. Schwann cell viability was evaluated and the most efficacious agent, N-acetylcysteine, was encapsulated into microparticles. Eluted samples of N-acetylcysteine from microparticles was evaluated for retained bioactivity.

RESULTS

100 µM N-acetylcysteine improved the viability of Schwann cells dosed with H2O2. 100 µM Microparticle-eluted N-acetylcysteine also enhanced Schwann cell viability.

CONCLUSION

We developed a Schwann cell culture model of iatrogenic nerve injury and used this to identify N-acetylcysteine as an agent to promote recovery. N-acetylcysteine was packaged into microparticles and demonstrated promise as a locally administrable agent to reduce oxidative stress in Schwann cells.

Effects of platelet-rich fibrin and dexamethasone on nerve regeneration after acute facial-nerve injury

BACKGROUND

Acute facial-nerve injury.

OBJECTIVE

To investigate the effects of platelet-rich fibrin (PRF) and dexamethasone on nerve regeneration.

MATERIALS AND METHODS

Thirty-six rats were randomly divided into six groups. Facial-nerve injury was created using a full-thickness incision in all groups except Group E. Next, primary anastomosis, PRF application, topical dexamethasone application, primary anastomosis with topical PRF and dexamethasone application, and no facial-nerve repair were performed in Groups A, B, C, D, and F, respectively. Clinical, functional, and structural improvements were evaluated at eight weeks.

RESULTS

The mean eye-closure movement score in Group B was significantly higher than that in Group F (p < .001). The mean whisker-movement score in Group B was significantly higher than that in Group F (p = .001). The mean amplitude of whisker movement in Group F was significantly lower than those in Groups A, B, C, and E, and the mean amplitude in Group D was significantly lower than that in Group E (p < .001). Furthermore, an improvement in nerve ultrastructure was observed in Group B.

CONCLUSION

PRF application has a positive effect on nerve recovery after anastomosis.

SIGNIFICANCE

Contribute to the literature to improve nerve regeneration.

Melatonin signalling in Schwann cells during neuroregeneration

It has widely been thought that in the process of nerve regeneration Schwann cells populate the injury site with myelinating, non–myelinating, phagocytic, repair, and mesenchyme–like phenotypes. It is now clear that the Schwann cells modify their shape and basal lamina as to accommodate re–growing axons, at the same time clear myelin debris generated upon injury, and regulate expression of extracellular matrix proteins at and around the lesion site. Such a remarkable plasticity may follow an intrinsic functional rhythm or a systemic circadian clock matching the demands of accurate timing and precision of signalling cascades in the regenerating nervous system. Schwann cells react to changes in the external circadian clock clues and to the Zeitgeber hormone melatonin by altering their plasticity. This raises the question of whether melatonin regulates Schwann cell activity during neurorepair and if circadian control and rhythmicity of Schwann cell functions are vital aspects of neuroregeneration. Here, we have focused on different schools of thought and emerging concepts of melatonin–mediated signalling in Schwann cells underlying peripheral nerve regeneration and discuss circadian rhythmicity as a possible component of neurorepair.

Sustained Release In Situ Thermogelling Hydrogel of Cerebrolysin for Treatment of Facial Nerve Axotomy in Rats

PURPOSE

The most essential principle in managing facial nerve (FN) injury is proper diagnosis and early treatment. This study evaluated local application of different concentrations and injection intervals of Cerebrolysin hydrogel (CBLH) for facial nerve axotomy (FNA) treatment. We hypothesized that local application of CBLH may provide a sustained release of Cerebrolysin and enhance neural regeneration.

METHODS

The authors implemented a randomized, controlled, blinded animal study. The sample was composed of the right FN. Functionally, eye-blink reflex was evaluated 2 and 4 weeks postoperatively. All rats were euthanized after 4 weeks, and nerve regeneration was evaluated histopathologically and immunohistochemically (IHC) with antibody against neurofilament (anti-NF) and S100 proteins. Descriptive and correlation statistics were computed, and the P value was set at .05.

RESULTS

The sample was composed of 72 adult male rats equally allocated into 8 groups. Groups I and V served as control groups and were injected with phosphate buffered saline once and four times, respectively. Rest of the groups were injected with 5%, 10%, and 15% CBLH once in groups II, III, IV and weekly in groups VI, VII, and VIII. CBLH showed statistically significant FN regeneration by enhancing Schwann and axonal growth compared to control group especially with single injection of 10%, 15%, and 5% 4-time injections, where the P value was less than .001. Significant improvement of eye-blink reflex was correlated with structural improvement associated with CBLH.

CONCLUSION

Finally, CBLH enhanced nerve regeneration and rehabilitation after FNA in rats. Therefore, it could be considered as an alternative treatment of FNA. More experimental and clinical trials should be considered to detect the effectiveness of CBLH in neural regeneration.

New Advances on Pathophysiology of Diabetes Neuropathy and Pain Management: Potential Role of Melatonin and DPP-4 Inhibitors

Pre-diabetes and diabetes are growing threats to the modern world. Diabetes mellitus (DM) is associated with comorbidities such as hypertension (83.40%), obesity (90.49%), and dyslipidemia (93.43%), creating a substantial burden on patients and society. Reductive and oxidative (Redox) stress level imbalance and inflammation play an important role in DM progression. Various therapeutics have been investigated to treat these neuronal complications. Melatonin and dipeptidyl peptidase IV inhibitors (DPP-4i) are known to possess powerful antioxidant and anti-inflammatory properties and have garnered significant attention in the recent years. In this present review article, we have reviewed the recently published reports on the therapeutic efficiency of melatonin and DPP-4i in the treatment of DM. We summarized the efficacy of melatonin and DPP-4i in DM and associated complications of diabetic neuropathy (DNP) and neuropathic pain. Furthermore, we discussed the mechanisms of action and their efficacy in the alleviation of oxidative stress in DM.

The efficacy of corticosteroid after facial nerve neurorrhaphy: a systematic review and meta-analysis of randomized controlled trial

OBJECTIVES

The benefit of corticosteroids following facial nerve neurorrhaphy in the setting of complete transection is questionable. This systematic review and meta-analysis aimed to evaluate corticosteroid efficacy on facial nerve regeneration and functional recovery after complete disruption and neurorrhaphy.

METHODS

Randomized controlled trials on both human and animal models from Ovid MEDLINE and Ovid EMBASE studying corticosteroid efficacy in complete facial nerve disruption followed by neurorrhaphy were included. Data were extracted and pooled for meta-analysis. The outcomes were evaluated from electrophysiology, histology, and functional recovery. However, no randomized controlled trial in human was performed. Possibly, performing human trials with histopathology may not be feasible in clinical setting.

RESULTS

Six animal studies (248 participants) met inclusion criteria. Electrophysiologic outcomes revealed no differences in latency (Standardized Mean Difference (SMD) = -1.97, 95% CI -7.38 to 3.44, p = 0.47) and amplitude (SMD = 0.37, 95% CI -0.44 to 1.18, p = 0.37) between systemic corticosteroids and controls. When analysis compared topical corticosteroid and control, the results provided no differences in latency (Mean Difference (MD) = 0.10, 95% CI -0.04 to 0.24, p = 0.16) and amplitude (SMD = 0.01, 95% CI -0.08 to 0.10, p = 0.81). In histologic outcomes, the results showed no differences in axon diameter (MD = 0.13, 95% CI -0.15 to 0.41, p = 0.37) between systemic corticosteroid and control; however, the result in myelin thickness (MD = 0.06, 95% CI 0.04 to 0.08, p < 0.05) favored control group. When comparing systemic corticosteroid with control in eye blinking, the results favored control (MD = 1.33, 95% CI 0.60 to 2.06, p =  0.0004).

CONCLUSIONS

This evidence did not show potential benefits of systemic or topical corticosteroid deliveries after facial nerve neurorrhaphy in complete transection when evaluating electrophysiologic, histologic, and functional recovery outcomes in animal models.

Is Decorin a Promising New Agent for Facial Nerve Regeneration? An Experimental Study

OBJECTIVE

The aim of this study was to investigate the effects of systemic administration of decorin (DC) on facial nerve (FN) regeneration.

METHODS

A total of 32 female albino Wistar rats were divided into 4 groups: control (C) group: no bilateral FN neurorrhaphy (B-FNN), no DC application, sham-operated group: B-FNN without DC application, DC group: DC application without B-FNN, and B-FNN + DC group: B-FNN and DC application. Nerve conduction studies were performed before and after skin incisions at 1st, 3rd, 5th, and 7th weeks in all groups. The amplitude and latency of compound muscle action potentials were recorded. FN samples were obtained and were investigated under light microscopy and immunohistochemical staining. The nerve and axon diameter, number of axons, H score, Schwann cell proliferation, and myelin and axonal degeneration were recorded quantitatively.

RESULTS

In the sham group, the 3rd and 5th postoperative week, amplitude values were significantly lower than those of the B-FNN + DC group (p < 0.05). Nerve diameters were found to be significantly larger in the sham, DC, and B-FNN + DC groups than in the C group (p < 0.05). The number of axons, the axon diameter, and the H scores were found to be significantly higher in the B-FNN + DC group than in the sham group (p < 0.05). The Schwann cell proliferation, myelin degeneration, and axonal degeneration scores were significantly lower in the B-FNN + DC group than in the sham group (p < 0.05).

CONCLUSION

Electrophysiological and histopathological evaluation revealed the potential benefits provided by DC. This agent may increase FN regeneration.